Electrical fence charger



Dec. 7, 1948.

E. K. MALME ELECTRICAL FENCE CHARGER Filed Dec. 10, 1945 /iz v6.12 for [122er 7g2/me NV MQQN l [im @mmwkmw m Sui .wm S k n k 0\ i; n 2S E ma n Patented Dec. 7, 1948 ELECTRICAL FENCE CHARGER Elmer K. Malme, Chicago, Ill., assignor to Guard- It Manufacturing Co., Chicago, Ill., a corporation of Illinois Application December 10, 1945, Serial No. 634,060

3 Claims. (C1. 1v1- 97) VThis invention relates to an electrical apparatus' and particularly to an electric fence charging system. Electric fence chargers for periodically impressing a. high potential on wire fences are wellknown in the art. Such chargers comprise a step-up transformerand means for periodically closing the transformer primary circuit. The secondary may furnish as much as 3000 volts and is connected between ground and the fence to be charged. The primary of the transformer is generally adapted to be energized by some low voltage such as six volts. Included as part of the unit is a supply transformer, rectier and condenser which may be used to supply six volts direct current to the primary of the step-up transformer if a. power circuit such as 110 volt, 60 cycle is available. In the absence of such a power line connection, a six volt battery may be used as the energizing source.

It is understood that the six volts is merely exem-plary, and the voltage may have other values as desired. In any event, fence chargers are customarily made to be energized from an alternating current power line or local batteries. The entire charger is disposed in a metal case with the case itself acting as a ground for the charger system and being grounded to earth to provide a through circuit for the high voltage.

When a fence charger is connected for operation to a power line, it is possible that, in the course of time, the insulation will become defective. Under such conditions, a through circuit between the 110 volt power line and fence to be charged may be established. While the voltage normally impressed on a charged fence may be of the order of 3000 volts, the charger is normally incapable of providing any current of substantial magnitude. Fence chargers generally operate with currents with instantaneous peaks from 100 to 500 milliamperes and average current of the order of around milliamperes. In the event that a power line becomes connected to a fence-through a defect in the insulation of the fence charger apparatus, a dangerous condition may be created.

` It is customary to dispose the entire fence charger unit in a metal case, which case is the ground for the charger circuit components. However, to complete the entire fence charger circuit, areal ground from the metallic casing to earth is necessary. It may occur that the ground between the metallic .casing and earth becomes disconnected or has a high resistance. In such a case and assuming that a low resistance from fence to earth is present, a substantial portion put of the charger going to the fence is rendered impossible. In general, the invention contemplates the disposition in a portion of the output circuit of the charger of a device having a low potential break-down characteristic in excess of any normal power line potential. Such device may consist simply of a gaseous discharge glow lamp or .tube having a break-down potential in excess of any normal peak potential encountered in the power line but well below any fence charging potential. Thus, as an example, ii a volt power line. is used to supply the fence charger, then the gaseous discharge device may be so designed as to break down at a voltage of about volts.

:Inasmuch as the normal charging potential for the fence is well above this voltage, it follows that the. electric circuit for charging the fence will be substantially unimpaired. Because of the resistance in the fence charging circuit presented by the fence and ground, a, gaseous discharge device having a break-down potential of around 180 will never have suflcient potential available across the discharge device to maintain a disch-arge even if such a discharge is initiated by a high potential fence charging pulse. This is for a 110'vo1t power line. For other power line voltages,v different potential break-down values would be necessary.

A low potential gaseous discharge device, in addition to providing the selective voltage breakdown action, may also be used as a visual indicating means to show that the charger system is operating properly. Thus, every time a high voltage fence charger pulse occurs, a flash of light will be emitted by the lamp. It is possible to mount the lamp in the casing in such a manner that a window will permit the flash to be visible from the outside.

A further advantage resides in the use of a low potential gaseous discharge tube in the high voltage secondary circuit. As is well known, a glow tube has the property of tending to maintain a constant voltage across its terminals. This property is utilized to reduce ripples in the high voltage circuit due to ripples in the rectifier output.

A low potential gaseous discharge device may be conveniently disposed in one of the terminals of the secondary winding of the high Voltage transformer. Inasmuch as this transformer is normally connected between the casing, which is to be grounded, and the fence, it is possible to dispose the low potential gaseous dischargedevice either in the lead extending from the transformer secondary and the fence or the lead vextending from the transformer secondary lto the casing, which in this particular system would represent the ground.

For a more complete description of the invention, reference will now be made to the drawing wherein exemplary embodiments of the invention are disclosed, it being lunderstood `that :the invention itself is susceptible .to various modifications.

Figure 1 shows a circuit diagram of .a charging system vembodying the present invention with the metallic casing shown in dotted outline.

Figure 2 shows the secondary circuit of the high voltage transformer .and illustrates a modiiied form of the invention.

Referring now to the drawing, high voltage transformer lli is provided with secondary H having leads l2 and I3. These leadslare taken .at opposite ends of secondary winding Il and normally represent the low and high potential terminals of the winding respectively. Lead I3 may be taken at an lintermediate point `in secondary I/I to provide a lower fence charging voltage.

Transformer lil has lprimary I5, one terminal of which goes to rotary switch I6 having contacts I1, IS and i9 respectively. As is evident, contact i9 is an off contact and is grounded. Contact I3 may be connected ,by wire v20 to 'battery 2l having one terminal ygrounded 1at 22 if 'battery operation is to be desired.

Contact l1 may be used when power `line oper.- ationof the charger is desired. vTo this end, contact I1 is connected by wire '23 to terminal 24 of rectifier system l25 having its other terminal 26 grounded. Rectifier system .25 may be any type desired and is here shown as of the lbridge type having rectiiier elements 21. Any full :wave type is preferred because of vthe smoother output. Each rectier element may be of any type. Thus, a simple rectifying system utilizing copper oxide or selenium rectiers are available .on ythe mar.- ket. Bridge system Y25 has input 'terminals 29 and 30 to which may be connected secondary .3l of power transformer 32. IPower transformer 3-2 has primary 35 for connection to any suitable power line such as the 110 volt 60 cycle gener,- ally available. The grounds in the various 'instances represent a connection to ametalliccasing enclosing the entire `apparatus and ygenerally indicated by numeral 35. This casing itself may be grounded to the earth as shown at 36 to provide a fence charging terminal.

Output terminals 24 and 26 of bridge rectifier 25 are preferably connected to condenser 31 having a substantial capacitance. Other ,-ltering means may be provided. Thus, condenser 31, as one example, may have a capacitance .of several micro-farads. It has hitherto .been .customary to provide a capacitance of the order :of several thousand micro-farads. It will be noted that a terminal of .the rectifier vand condenser are grounded to the casing.

Primary I5 of high voltage transformer I0 has one terminal connected by lead 38 to grounded interrupter switch 39. Switch 39 may be any one of a number of types of switches, which periodically open and close. Thus, the switch may cooperate with the core of transformer I0 to maintain the switch in continuous operation. Inasmuch as sucnswitches ``are ,well known in the art, a detailed description thereof is deemed-to be urinecessary. As a rule, such switches have as part thereof a spring which permits the switch to operatefat-a relatively low frequency of the order of about 30 to 60 cycles per minute. Switch 39 may be Ashunted by condenser 40 to reduce arcing at the contacts.

Connected in the youtput fence charging circuit, here .shown .betweenlead l2 and ground, is glow discharge lamp 12. Lamp 42 may be any one of a number of neon or other gas lamps, which are adapted to break down and initiate a glow discharge `at 1a certain potential. '"lhllS,l :if [110 volts is applied to theferi-mary v0f ythe powertransformer, gas 4tube .42 may vbe so designed to breakdown :at about 180 volts. The exact 'value is unimportant, vsince this ,is well above fthe nor mal peak ina 1.150 volt line. If a 22,0 Yvolt :line were used, Alamp 42 vwould be so `desigggied ,as to break down at yaround 360 volts. As a rule, the running voltage is less than 4the starting voltage. In Jall cases. .it is preferred t0 have the voltage of the :lamp also Well above any .normal peak voltage yin the power line.

Shllnted across lamp 42 iscondenser 43 .having substantial capacitance. While this Andenser is lnot essen-tial, -it .does have a desirable `-acticn on the wave form of the output voltage. Thus, when the .lamp breaks ydown ,and conducts, the condenser becomes charged. In practice, condenser 43 may have a capacitance [of about ,l micro-fared. This value, however, is not Vcritical and-may .be vvaried lWithin Wide lim-its 0r the condenser `may -be omitted.

The .gas discharge lamp .is preferably designed so 4that it may handle the Current normally desired for charging the fence. Thus ,|the,lar np may be designed so that -it may readily pass a Acurrent with instantaneous peaks from 1.00 to 1 590 trulliF amperes without damage. -It is well :known that such lamps have no -xed current for operation, so :that the .current passing through it may vary over iwide limits. However, .the 1positive resistance of the char-sine circuit Twill ,keep vthe lamp cur)- rent to -a safe value.

if desired, lamp Vi2 may 'be disposed in lead |3 or 1 3', as shown in Figure 2, or glamps may be disposed in every one .of the transformer leads.

'It is 4 cl-ear that the `high voltage secondary Winding lis connected Ain vseries to a gas tube ybetween the Casing and .other fence `charging ter.- minal.

For protection against a bad `ground .between casing 35 .and .earth 36, high -potential -.gas tube 4,5 may .be disposed between one terminal of Yprimary `33 and metallic casing 35. As shown here, one side of the power line is grounded. `It 4is immaterial to which terminal of primar-y 3,3 tube 4 5 is connected. Tube 4,5 will break down and conduct at potentials `somewhat below nonna-l fence charger potentials generated iby secondary Isl ibut ,of the Same general order. Thus, if sec.- ondary `H generates potentials of the ,order of around Y30H0 volts, tube 45 may breakdown at a potential Aof around G volts or more.

4In theevent that the fence charger iunit isoperating and the ground between casing :3;5 .and

earth 36 is impaired, any high potential tending to break down the insulation of transformer 32 will be adequately handled by gas tube 45. In such case, a high potential circuit from terminal I3 (or |3) to a fence, then to earth, then through the power line to primary 33 through gas tube 45 and casing 35 may be traced. From casing 35, the circuit will continue through to terminal I2.

It will be evident that, with the power line grounded to the casing, the peak voltage present in the power line will be insuilicient to break down the protective low potentia1 lamp and complete a circuit through to the fence. When the low potential lamp is conducting in response to a high potential surge from transformer secondary H, a connection from the power line to the fence is momentarily established. However, the through connection is promptly broken when the high potential surge has passed, Thus, momentary connections between the power line and the fence may exist under the worst conditions. Such momentary connections are not objectionable and will have little or no eil'ect.

It has been found that the voltage regulating action of the low potential glow discharge tube permits condenser 31 to have substantially less capacitance than would normally be the case with no lamp and still provide an output charging voltage having a low percentage of ripple voltage.

In operation, interrupter 39 closes the primary circuit of high potential transformer I for a short time and keeps the circuit open for a much longer time, The interrupter cycle is much longer than any power cycle from the power line.

It is understood that, if battery operation is desired, the power line connection is not used. The battery may be disposed outside of casing 35.

What is claimed is:

1. A fence charger comprising voltage transformer means having an input winding for energization from an alternating current power line at normal potential for domestic use, said power line having one side thereof grounded, said transformer means having a high potential output winding for providing a fence charging potential of an order substantially greater than any normal power line potential, a casing including a Cil metallic portion for enclosing said fence charger elements, said metallic portion constituting one fence charger terminal, a second fence charger terminal adapted to be connected to a fence to be charged, said metallic casing portion being adapted to be connected to earth for providing a return circuit for fence charging, and a gas tube connected between said input winding and said case, said gas tube being conducting for potentials below fence charging potentials but above any normal potential in the in-put winding whereby, if said connection between earth and said metallic casing becomes impaired, a fence charging circuit may be completed through said gas tube without impairing normal insulation.

2. The structure of claim 1 wherein a second gas tube is connected in series with the high potential output winding, said second gas tube being non-conducting at potentials larger than but of the same order as normal peak power line potentials but conducting at potentials in excess thereoi, said second gas tube being adapted to become conducting at a potential substantially lower than the potential at which the first-named gas tube becomes conducting and wherein a condenser is shunted across said second gas tube.

3. The structure of claim 1 wherein a second gas tube is connected in series with the high potential output winding, said second gas tube being non-conducting at potentials larger than but of the same order vas normal peak power line potentials but conducting at potentials in excess thereof, said second gas tube being adapted to become conducting at a potential substantially lower than the potential at which the first-named gas tube becomes conducting.

ELMER K. MALME.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 2,090,199 Heidger Aug. 17, 1937 2,196,046 Willis Apr. 2, 1940 2,265,039 Harder Dec. 2, 1941 2,318,832 Roach May 11, 1943 2,415,944 Fagen Feb. 18, 1947 

